Jet mill



C. M. TROST Oct. 2, 1956 JET MILL 2 Sheets-Sheet Filed May 19, 1953 z i nv. ll.

INVENTOR. CONRAD M 713037" Oct. 2, 1956 c. M! TROST 2,765,122

JET MILL Filed May 19, 1955 2 Sheets-Sheet '2 INVENTOR. CONRAD M 77%057' JET MILL Conrad M. Trost, Moorestown, N. J.

Application May 19, 1953, Serial No. 355,937

7 Claims. (Cl. 241-40) This application refers to a fluid jet mill for comminuting dry materials and it constitutes a continuationin-part of my co-pending application Serial No. 229,593, now Patent No. 2,704,635, issued March 22, 1955.

In applying the mill of my said co-pending application to certain uses, particularly to the grinding of coal on board a railway locomotive, it has been found necessary to provide a specific form thereof which is capable of being accommodated within a relatively small space and yet providing substantially undiminished grinding and classifying capacity. Accordingly, certain modifications in the structure disclosed in said co-pending application were necessary and it is the purpose of the present invention to provide such modifications.

Therefore, a primary object of the invention has been to provide a device for grinding dry solid material, particularly bituminous coal, which is sufliciently compact to be capable of being received into a relatively small space.

A further object of the invention has been to provide a device, as aforesaid, which has a high degree of grinding capacity and which is particularly adaptable to bituminous coal, or similar materials.

A further object of the invention is to provide a device, as aforesaid, in which the back pressures arising in the classification zone and also arising in the dscharge from the mill may be relatively high with respect to the pressure under which the material is fed into the grinding chamber without materially injuring either the capacity of the mill or its efiiciency in classification.

A further object of the invention has been to provide a device, as aforesaid, which can be readily modified to utilize either anvil grinding or jet grinding.

A further object of the invention is to provide a device, as aforesaid, which will be sturdy and free from high maintenance requirements.

A further object of the invention is to provide a device, as aforesaid, which has no moving parts.

A further object of the invention is to provide a device, as aforesaid, wherein the classification of ground material will be attained with a high degree of accuracy.

Other objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general sort upon a reading of the following disclosure and inspection of the accompanying drawings.

In the drawings:

Figure 1 is a view of a preferred form of the apparatus shown in central, vertical cross-section.

Figure 2 is a sectional View taken along the line IIII of Figure 1.

Figure 3 is a fragmentary, sectional view similar to Figure 1 but showing a modification of the invention.

Figure 4 is a section taken on the line IVIV of Figure 1.

Figure 5 is a horizontal section view showing a further modification.

Referring now to the drawings in detail, there is shown in Figure 1 an elongated casing, or grinding housing, 1,

2,765,322 Patented Oct. 2, 1956 the same being of either cylindrical or rectangular crosssection, having an anvil 2, located at and closing one end thereof and a plug 3 located at the other end of said casing. Said anvil 2 is held in position by any convenient means, as the set screw 4. Plug 3 is held in position by any convenient means, as the set screw 6.

A conduit 7 terminating in a nozzle 8 extends through the plug 3 from a point externally of the apparatus and is operatively associated with a feeding device 5, as a hopper. Said conduit 7 may be connected to any convenient source of grinding fluid under pressure, such as either compressed air or steam. A venturi block 9 is positioned Within the casing 1 intermediate the nozzle 3 and the anvil 2 and is normally somewhat closer to said nozzle. An internal passageway 11, having a flared entry end 12, is provided through said venturi block 9 co-axial with the said nozzle 8 and with the casing 1.

An off-take conduit 13, of cross-section preferably as shown in Figure 4, extends upwardly from the opening 15 in the casing 1 at a point therein intermediate the venturi block 9 and the anvil 2. In the particular embodiment of the invention here shown, said off-take conduit is substantially adjacent the discharge end of said passageway 11 in said venturi block 9, and somewhat spaced from the face of the anvil 2, but this may vary according to the kind of material being handled.

A first orienting conduit 14 is placed above said offtake conduit 13 and connected thereto by flanges 1'7 and 29 in a known manner. Said first orienting conduit curves rather sharply, as about in a direction away from the nozzle and is connected to a second orienting conduit 16 by flanges 18 and 25. Said second orienting conduit curves, as about 90, in a direction away from the grinding chamber 10 and provides, in combination with the conduit 14, an offset and reverse curve. A classifying section 19 is substantially semi-circular and connects to the second orienting conduit 16 by the flanges 21 and 22. Said classifying conduit 19 may be of a variety of cross-sectional shapes, including round, elliptical and trapezoidal, as set forth in detail in my Patent No. 2,704,635, issued March 22, 1955, but is preferably round or elliptical. Said classifying conduit has a discharge opening 23 which communicates through a discharge conduit 26, having an entry throat 24, with any desired point of use or storage of the material withdrawn from the classifying conduit.

A return conduit 27, of substantially circular crosssection, is connected at one end to the classifying conduit 19 by the flanges 28 and 29. The other end of said return conduit 27 is connected to the casing 1 and communicates with the interior of the chamber 32 through a return opening 31, located between the plug 3 and the venturi block 9. The return conduit 27 may be straight, as shown.

In Figure 3 there is shown a modification of the device in which the anvil 2 is replaced by a plug 36 through which extends a conduit and nozzle assemblage 37 which is placed in opposing, co-axial, relationship with the nozzle 8. In all other respects this apparatus is the same as that described in connection with Figures 1, 2 and 4.

In Figure 5 there is illustrated a further modification in which an anvil 41 is placed within the grinding chamber 19 substantially under the off-take conduit whose opening 15 is indicated by broken lines in said Figure 5. Fluid conducting conduits 42 and 43, for delivering high velocity jets, are added to the structure of Figure 3 and each of these jets, together with the main grinding and feeding conduit 7, direct streams of grinding fluid against the sides of the anvil 41. Partially comminuted material to be ground may be fed through any or all of the conduits 37, 42 and 43 in addition to the feeding thereof through the conduit 7 or, in instances where the material is of maximum grinding difficulty, it may be fed into the device only through either or both of the conduits 7 and 37, and the auxiliary jets will function to drive material circulating through the grinding chamber 143 against the several faces of the anvil 41. Other parts of the device shown in Figure 5 are the same as those shown in connection with Figures 1, 2 and 4, and are numbered correspondingly. Likewise, the device discharges through a discharge opening and through classification means the same as shown in Figure l and returned material reenters the device for further grindin through the return opening 31.

Operation A mixture of partially comminuted material, as bituminous coal, with a grinding fluid, as steam or air, is introduced into the device from the conduit 7 through the nozzle 3. it passes through the venturi passageway 11 and is driven at a high velocity against the face of the anvil Z. The material is largely shattered and that which is sufficiently fine to be carried by the fluid stream passes out of the grinding chamber 16 through the opening 15 into the first orienting conduit 14. The reverse/turn in the conduits i4 and 16 provides an initial classifying action in that the coarser material will partially separate in each turn from the finer material and thus will tend to gather on the radially outermost wall of the classifying section 1d somewhat more quickly than is possible in previously known devices. Thus, theuse of the reversely curved conduit enables the classifying chamber to be materially smaller than in those cases where the curve is all in one direction. As the material moves through the classifying chamber 19, the coarser portion thereof continues to gather at the radially outermost wall so thatby the time a given portion thereof reaches the zone adjacent the outlet opening 23, only the finer materials within a pre-determined classification size range are adjacent the radially inner Wall of the classification chamber. Inasmuch as the return conduit 27 is of somewhat smaller cross-sectional area than that of the classification chamber 19, that portion of the carrying fluid which is adjacent the inner wall of the classification chamber will be caused to travel out through the Opening 23 into the discharge conduit 26. Such fluid will carry with it such part of the shattered material entrained therein as is able to follow said carrying fluid around the relatively sharp corner as said fluid passes from the classification chamber to the discharge conduit 26. The remainder of the carrying fluid and the larger particles of the solid load therein return through the return conduit 27 to the chamber 32 where said fluid and said returned particles are again picked up by the fluid entering through the nozzle 8 and driven, together with the new materialbeing introduced, against said anvil and the cycle is repeated.

Axial adjustment of the conduit 7 may be made by loosening the set screw s in order to position the nozzle 8 properly with respect to the opening 31 and the flared entry 12 of venturi passageway 11 for effecting the most efficient return of both the carrying fluid and the oversized particles into the grinding stream. Normally, such position will be that shown in Figure 1, namely, where the end of the nozzle 3 extends slightly more than half way past the center of the opening 31.

Similarly the anvil 2 may be positioned longitudinally of the casing 1 by suitable manipulating of the set screw Such positioning will be in terms of the distance of its face from the opening 15 and will vary according to the type of material being ground and to the fineness with which it is intended to be ground, which information may be derivcdfor given instances by the usual methods.

The form of the invention shown in Figure 3 utilizes a pair of opposed jets in place of the jet and anvil combination of the structure shown in Figure 1 and has certain advantages in some circumstances, but the reverse curve provided by the conduits 14 and 16, and'fhe operation thereof, remains the same as above described with respect to Figure 1. In this form, material may be introduced through either of said jets, or through both of them, as preferred, to accommodate the apparatus to specific services.

In the form shown in Figure 5, the initial shattering of the material entering from the conduit 7 takes place against the opposed face of the anvil 41. However, such material will circulate around through the grinding chambar it ior to being drawn upwardly through the opening 2.5 (Figure I). This will be particularly true of the larger particles which will tend not to move upwardly with the fluid stream as readily as the smaller particles. Thus, the further jets 37, 42 and 43 will hurl such particles nst other faces of the anvil 41 and further the shattering thereof. if desired, further supplies of solid material may be introduced through one or more of the conduits 37, a2 and 43. Alternatively, the material may be introduced only through conduits 37, 42 and 43 and jet 8 left free to carry only the return load from return conduit 27. This will be somewhat more efficient in those cases where there is a high volume of recirculating material. Such multiple introduction of material may be used in a wide number of cases and will be particularly useful in those instances where the material shatters relatively easily but it is not possible for any one jet to carry as high a load of material as the classifying chamber can handle.

In all three forms of the mill here shown, the grinding chamber is kept relatively short so that the material introduced thereinto through the nozzle 8 strikes either the anvil or the opposing jet with a maximum of force. Thus, it is possible to utilize a relatively low energy input with a maximum of efliciency and the efiectiveness of the grinding does not seriously sufler. The reverse bend in the conduit leading to the classification chamber effects certain preliminary classification so that the total conduit length from the opening 15 to the opening 31 may be kept at a minimum. This effects further savings in energy and space requirements, without permitting classification effectiveness to be materially diminished. Thus, theobjects and pulposes above set forth have been accomplished.

While certain specific embodiments of the invention have been set forth in detail for illustrative purposes, it will be recognized by those skilled in the art that various other modifications may be made without departure from the principles of the invention, and hence the appended claims are to be interpreted as including such variations excepting as such claims may by their own terms expressly limit otherwise.

What is claimed is:

1. In a fluid energized pulverizing device for partially comrninuted material, the combination comprising: an elongated grinding housing; jet means directed substantially parallel with the lengthwise axis of. said housing for introducing grinding fluid and partially comminuted material into one end thereof, and means opposing said jet providing a medium against which said fluid, and material carried thereby, impinges; an off-take opening from said housing, and a return opening to said housing adjacent said jet; a substantially semi-circular classifying chamber spaced from said grinding housing; a reversely curved conduit connecting said elf-take opening with one end of said chamber and a return conduit of cross-sectional area smaller than that of said chamber connecting the other end of said chamber with said return opening in said grinding housing; and a discharge opening in the radially inner side of said classifying chamber at a point thereon near said return conduit.

2. The apparatus defined in claim 1 wherein said opposing means constitutes an anvil having a face substantially perpendicular to the flow of fluid from said jet means and positioned so that said off-take opening is between said jet means and said face.

3. The apparatus defined in claim 1 including also: a venturi block within said grinding housing intermediate said return opening and said ofi-take opening and having a passageway therethrough substantially co-axial with said jet means.

4. The apparatus defined in claim 1 wherein said opposing means constitutes a nozzle co-axial with said jet means and placed in opposition thereto.

5. The apparatus defined in claim 1 wherein said 0pposing means constitutes an anvil having a face thereof substantially aligned with said oflF-take opening and positioned perpendicularly to the axis of said jet means, and also having a plurality of other faces; and means conducting a jet of grinding fluid in a direction perpendicularly against each of said other faces.

6. The apparatus defined in claim 3 including a plug having an aperture therein at one end of the housing, said jet means extending through the aperture and partially beyond the inner face of the plug, said return opening being located between the plug and the venturi block.

7. In a fluid energized pulverizing device for partially comminuted material, the combination comprising: an elongated grinding housing; jet means directed substantially parallel with the lengthwise axis of said housing for introducing grinding fluid and partially comminuted material into one end thereof, and means opposing said jet providing a medium against which said fluid impinges; an ofi-take opening from said housing and a return opening to said housing adjacent said jet; a substantially semi-circular classifying chamber spaced from said grinding housing; a reversely curved conduit connecting said off-take opening with one end of said chamber and a return conduit connecting the other end of said chamber with said return opening in said grinding housing; and a discharge opening in the radially inner side of said classifying chamber at a point thereon near said return conduit.

References Cited in the file of this patent UNITED STATES PATENTS 2,237,091 Stephanofi Apr. 1, 1941 2,487,088 Andrews Nov. 8, 194-9 2,521,000 Crowley Sept. 5, 1950 2,672,296 Venable Mar. 16, 1954 

